1. Field of the Invention
This invention generally relates to the quality of flat glass produced from a molten glass mass and, more particularly, to a cleaning apparatus for removing uneven and crusty deposits from the surfaces of conveying rolls.
2. Description of the Prior Art
In the production of flat glass, it is customary to produce a continuous ribbon of glass from a molten glass mass and convey this newly formed ribbon through an annealing lehr. One of the primary purposes of conveying the newly formed glass ribbon through the lehr is to cool the ribbon from the hot plastic condition in which it emerges from the forming area to a rigid glass ribbon at approximately ambient temperature while producing a controlled permanent stress pattern therein. In a conventional annealing process, temperatures in the lehr may range from about 1300.degree. F. (704.4.degree. C.) at its entrance end to about 400.degree. F. (204.4.degree. C.) or less at its exit end. The newly formed glass ribbon is in a softened plastic condition, and it remains in this condition as it enters the entrance end of the annealing lehr. Consequently, the newly formed glass ribbon is subject to a defect known in the art as "roll print". Roll print, characterized by broad band distortion such as random surface rub marks, fissures and in some cases even fractures, is caused by mechanical contact of the softened, plastic glass ribbon with the conveyor rolls. The rolls may have uneven and crusty deposits on their surfaces which imprint on the soft undersurface of the newly formed glass ribbon.
In the case of annealing lehr conveyor rolls, especially those rolls adjacent the entrance to the lehr, the uneven and crusty deposits are thought to be formed on the surfaces thereof by the carryover of vapors from the glass forming process which condense and deposit themselves on the rolls as a crusty layer of nonuniform thickness, as well as by the carryover and transfer of foreign matter adhering on the soft undersurface of the glass ribbon.
Cleaning apparatus such as that disclosed in assignee's U.S. Pat. No. 4,042,364, issued on Aug. 16, 1977, has been used successfully to remove impacted crusty deposits from the surfaces of moderately encrusted conveyor rolls. However, such cleaning apparatus must be of heavy construction to provide the brushing forces required to remove deposits from heavily encrusted conveyor rolls. Since the available working space within a lehr is minimal, i.e. the space between the lehr rolls and the floor is of a very limited height, use of such an apparatus may not be feasible in all circumstances. Accordingly, it is desirable to provide a simple, efficient off-line roll cleaning apparatus for those rolls requiring greater cleaning effort.